Formula for Representing Problem Decomposition

A complex computational problem is broken down into three distinct, smaller parts to make it easier to solve. Using the standard formal notation for problem decomposition, which of the following correctly represents the set of these three resulting parts?

When an initial problem, denoted as $p_0$, is broken down into a series of n smaller parts, the standard formal notation used to represent the collection or set of these resulting parts is ____.

In the formal notation for problem decomposition, the expression {p_1, ..., p_n} signifies the specific, ordered sequence in which the sub-problems derived from an initial problem p_0 must be solved.